This invention relates to measurement systems, and more particularly, to capacitance measurement systems.
Many forms of prior art capacitance measurement systems utilize a capacitive bridge configuration to produce a signal representative of the relative capacitances associated with sensor and reference capacitors in the bridge. Other forms in the prior art include systems exemplified by U.S. Pat. No. 3,048,775 wherein a capacitive sensor is configured in the feedback path around an a.c. amplifier driven by a reference a.c. signal, and wherein the amplifier output is demodulated using a diode detector.
While such prior art capacitance measurement systems are suited for certain uses as accelerometers, scales and balances, proximity detectors, linear and angular position sensors, and pressure transducers, the prior art systems are substantially limited in accuracy and sensitivity of their respective measurements due to a number of factors, including temperature variation, stray or leakage capacitance, nonlinearities in the transducer configurations, noise, and drift. Furthermore, many prior art systems are limited to certain operational frequencies.
It is an object of the present invention to provide a capacitance measuring system wherein a signal is generaged which is a predetermined function of the capacitance of a sensor capacitor.
A further object is to provide a capacitance measuring system which is relatively insensitive to temperature variation, stray or leakage capacitance, noise, drift and operational frequency.